Field of the Invention
The invention relates to a data decoding apparatus and a method for decoding a serially transmitted signal thereof. Particularly, the invention relates to the method to detect a plurality boundaries of the serially transmitted signal without information about a clock frequency of a transmitter for encoding the serially transmitted signal.
Description of Related Art
For transmitting data with serially transmitted signal, a synchronous data transmission scheme and an asynchronous data transmission scheme are provided in convention art. Please referring to FIGS. 1A and 1B, wherein FIG. 1A illustrates a block diagram of the synchronous data transmission scheme, and FIG. 1B illustrates a block diagram of the asynchronous data transmission scheme. In FIG. 1A, a transmitter 110 and a receiver 120 are provided, and the transmitter 110 is coupled to the receiver 120. The transmitter 110 transmits a clock signal CLK and a serially transmitted signal DS to the receiver 120. The serially transmitted signal DS and the clock signal CLK are synchronous, and the receiver 120 can decode data carried on the serially transmitted signal DS according to the clock signal CLK.
In FIG. 1B, FIG. 1B provides a transmitter 130 and a receiver 140. The transmitter 130 is coupled to the receiver 140, and the transmitter 130 encodes transmitting data according to a clock signal CLKT for generating a serially transmitted signal DS. The transmitter 130 transmits the serially transmitted signal DS to the receiver 140. The receiver 140 can decode the serially transmitted signal DS to obtain the transmitting data according to a clock CLKR. It should be noted here, the clock CLKR of the receiver 140 is generated according to a clock frequency of the clock signal CLKT of the transmitter 130.
Such as that, in both of the synchronous data transmission scheme and the asynchronous data transmission scheme of conventional art, the receiver needs to know the clock frequency of the clock signal of the transmitter. Furthermore, it is required that the transmitter must have high bit rate accuracy. Specially, in high-speed universal serial bus (USB), the required accuracy of the transmitter is 480 Mbps+−0.05% (500 ppm).